Identification of individual and few layers of WS2 using Raman Spectroscopy

Ayse Berkdemir, Humberto R. Gutiérrez, Andrés R. Botello-Méndez, Néstor Perea-López, Ana Laura Elías, Chen Ing Chia, Bei Wang, Vincent H. Crespi, Florentino López-Urías, Jean Christophe Charlier, Humberto Terrones, Mauricio Terrones

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The Raman scattering of single- and few-layered WS2 is studied as a function of the number of S-W-S layers and the excitation wavelength in the visible range (488, 514 and 647 nm). For the three excitation wavelengths used in this study, the frequency of the A 1g (Γ) phonon mode monotonically decreases with the number of layers. For single-layer WS2, the 514.5 nm laser excitation generates a second-order Raman resonance involving the longitudinal acoustic mode (LA(M)). This resonance results from a coupling between the electronic band structure and lattice vibrations. First-principles calculations were used to determine the electronic and phonon band structures of single-layer and bulk WS2. The reduced intensity of the 2LA mode was then computed, as a function of the laser wavelength, from the fourth-order Fermi golden rule. Our observations establish an unambiguous and nondestructive Raman fingerprint for identifying single- and few-layered WS2 films.

Original languageEnglish (US)
Article number1755
JournalScientific reports
StatePublished - 2013

All Science Journal Classification (ASJC) codes

  • General


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